JPS6124681A - Frame for car of motorcycle, etc. - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a frame for a vehicle such as a motorcycle or a tricycle that uses a square pipe with a square cross section.

[Technical background of the invention and its problems]

In recent years, there has been a trend to use square pipes with a square cross section as frames for motorcycles instead of conventional round pipes, as shown in, for example, Japanese Patent Application Laid-open No. 58-145584 or Japanese Utility Model Application No. 58-164987. It is in. this is,
In addition to its appearance, square pipes are stronger against twisting, and in a typical narrow frame, the area that faces the force from a certain direction is larger than that of a round pipe. For example, the section modulus at the point where the maximum stress occurs due to bending is larger than that of a round pipe, which is advantageous in terms of strength.

However, in the case of recent wide frames (lateral frames), the square vibrator is not only subject to bending moments around the left and right axes of the car body, but also bending moments around the top and bottom axes are approximately the same amount due to vertical (up and down) loads. It has become clear through analysis by the present inventors that this phenomenon occurs.

In this way, when bending moments of approximately the same value act simultaneously around both the top, bottom, left and right wheels of a square pipe, the location where the maximum stress occurs is at the corner of the square pipe, and at this time, the maximum stress generation point of the square pipe, That is, when the section modulus of the corner portion is compared with that of a round pipe having the same cross-sectional area and second moment of inertia, the square pipe becomes smaller than the round pipe, which is undesirable in terms of the strength of the frame. Therefore, in order to give a frame made of square pipes the same strength as a frame made of round pipes, it is not enough to compare the moment of inertia of area, but rather how to reduce the stress applied to the corners of the square pipes. It became clear that this is important.

In addition, in order to increase the strength of the frame,
Frames that use hexagonal pipes for the tank rail and down tube are known, but in the case of this frame, it is necessary to secure a flat surface on the top surface of the down tube and tank rail to place the engine and fuel tank. First, the sharp corners are exposed on the side of the frame, which makes it look more strange than conventional square pipes, and it spoils the image of square pipes.

[Purpose of the invention]

The present invention is based on these circumstances,
To provide a frame for a vehicle such as a motorcycle, which can increase the strength and rigidity of a square pipe frame against longitudinal and lateral loads, can maintain the image of a square vibrator, and is advantageous in appearance.

[Summary of the invention]

In other words, in order to achieve the above object, the present invention comprises a frame made of square pipes, and at least one set of diagonally opposing corner parts of the square pipes is provided with a side surface of the square pipe and a side surface connected to the side surface of the square pipe. The square pipe is characterized in that a sloped wall section connecting the upper and lower surfaces obliquely is formed, and the square pipe is arranged with its flat side facing the side of the vehicle body.

[Embodiments of the invention]

An embodiment of the present invention will be described below based on FIG. 1 and FIG. M2 in which the present invention is applied to a frame for a motorcycle.

Fig. 1 shows a cradle-type wide frame made of aluminum alloy, for example, and a steering head pipe 1 located at the front end thereof has a pair of left and right tank rails 2, 2 extending in a straight line toward the rear, and these tank rails 2. , 2, a pair of left and right down tubes 3 extending rearward and downward below the tubes 3.
, 3 are welded. The tank rails 2, 2 and the down tube 3.3 protrude on both left and right sides immediately after the steering head pipe 1, and the rear ends of these tank rails 2, 2 and the down tube 3.3 are connected to the brackets 4, 4. are connected by.

Left and right seat rails 5.5 extending rearward are welded to the middle of the tank rails 2, 2, and a backstay 6.6 is installed between these seat rails 5.5 and the brackets 4, 4. has been done.

A fuel tank 7 is placed on the upper surface of the front half of the tank rails 2, 2 and the seat rail, and a space surrounded by the tank rails 2.2 and the down tube 3. is equipped with engine 8.

By the way, the tank rails 2, 2 and down tube 3.3 are square pipes with a rectangular cross section made of extruded or pultruded aluminum alloy, as shown in FIG. 2 representatively of the tank rail 2°2 side. 9, and this square pipe 9 is placed vertically with its long axis along the vertical direction of the vehicle body. The square pipe 9 has flat surfaces 10a, 10b, 10c on both sides of the top, bottom, right and left.
, 10d, and the rectangular portion of the square vibrator 9 has a flat sloped wall portion 11 that obliquely connects the left and right ends of the upper surface 10a and the lower surface 10b, and the upper and lower ends of the left and right side surfaces 10c and 10d.・is formed. Therefore, the square pipe 9 of this embodiment has a rectangular cross-section with each corner of the square cut diagonally, and such a square vibe 9 has a side surface 10c or 10d facing the side of the vehicle body. It is located.

The wall thickness t of the corner vibrator 9 is uniform in the circumferential direction, and the cut amounts a and b of each corner in the vertical and horizontal directions are the length A of the upper and lower surfaces 10a and 10b, and the left and right sides 10c. , are formed uniformly over a length B of 10d.

Next, the operation of the above configuration will be explained.

In the case of the above-mentioned wide frame, as mentioned in the previous section [Technical background of the invention and its problems], the square vibrator 9
Due to the vertical load, a bending moment around the left-right axis 01-01 of the car body and a bending moment around the vertical axis 02-02 of the car body act simultaneously on the square pipe 9, so the point where the maximum stress occurs on the square pipe 9 is at the diagonal line 03. -03 will be each corner on the top.

In this case, in the frame having the above configuration, the point where the maximum stress occurs is not formed at an acute corner but at the sloped wall portion 11 having a certain area; in other words, it is made flat; The stress applied here is dispersed over a wide range, and as a result, the stress generated at the intersection with the diagonal line 03-03 is reduced. Therefore, if the cross-sectional area of this square pipe 9 is made the same as that of the conventional square pipe, both the strength and rigidity of the frame can be improved. Especially when considering the vertical and horizontal loads on this square vibe 9, the rigidity and strength can be improved. The cross-sectional shape of this embodiment is optimal in achieving the balance.

Moreover, if the square pipe 9 having the above shape is used, the flat side surface 10c or 10d faces the side of the vehicle body, so the image of the conventional square pipe can be maintained, which is advantageous in terms of appearance. There are advantages.

In carrying out the present invention, the above-mentioned square pipes are not limited to tank rails and down tubes, but may also be used, for example, in seat rails and other cross pipes. Since the directions and sizes are different, it is not necessary to form slope walls at all corners; for example, as shown in FIG. 3, slope walls 11.11 are formed only at one diagonally opposite corner. Or, as shown in Fig. 4, slope walls 11/
. . . may be provided.

Furthermore, the vehicle according to the present invention is not limited to a motorcycle, but may be a tricycle having two rear wheels.

(Effects of the Invention) According to the present invention described in detail above, the point where the maximum stress occurs is not formed at an acute corner, but is formed at a slope wall portion with a certain area and is made flat, so that The stress will be distributed over a wide range.As a result, the stress applied to the square pipe will be reduced, and if the cross-sectional area of the square pipe is the same as the previous square pipe, the weight will be increased. It becomes possible to improve both the strength and rigidity of the frame without any problems.

Moreover, since the flat side of the square pipe faces the side of the vehicle body, the image of the conventional square pipe can be maintained as is, which has the advantage of being advantageous in terms of appearance.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a side view of the frame, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIGS. 3 and 4. FIG. 3 is a sectional view showing another embodiment of the present invention. 9... Square pipe, 10a... Upper surface, 10b... Lower surface, ioc. 10d...Side surface, 11...Slope wall portion.

Claims (1)

[Scope of Claims] In a vehicle frame using a square pipe with a square cross section, at least one set of diagonally opposing corners of the square pipe has a structure between a side surface of the square pipe and an upper surface and a lower surface continuous to the side surface. 1. A frame for a vehicle such as a motorcycle, characterized in that the square pipe is arranged with its flat side facing the side of the vehicle body.